Background: Abnormal thyroid function was shown in children with Down syndrome (DS). This study was undertaken in order to specify these anomalies.
Population and methods: Thyroid function of 105 children with DS aged from 3 months to 20 years was studied by evaluation of serum concentration of thyrotropin, free T4 (FT4), free T3 (FT3) and reverse T3 (rT3). Each DS child was matched to a control of the same age.
Results: The mean concentration of thyrotropin of children with DS was increased while the mean concentration of rT3 of the DS children was significantly decreased compared with the controls, as was the ratio rT3/TSH. When DS children are split into two groups, those with and those without increased thyrotropinemia, a significant decrease in the ratio rT3/TSH appeared in DS children with increased thyrotropinemia whereas there is no difference between these two groups regarding to level of FT4, FT3, rT3 and zincemia. However, in all DS children serum zinc levels were lower than in controls. Thyrotropin levels rapidly normalized after thyroxin treatment.
Conclusion: One half of the children with DS have increased thyrotropinemia and all have a decreased rT3.